The subject invention is directed toward the art of tube fittings and, more particularly, to an improved phase controlled, sequential gripping tube fitting.
The general form of tube fitting with which this invention is concerned is described and claimed in the following series of U.S. patents which are incorporated herein by reference:
U.S. Pat. No. 2,484,815 issued Oct. 18, 1949
U.S. Pat. No. 3,075,793 issued Jun. 29, 1963
U.S. Pat. No. 3,103,373 issued Sep. 10, 1963
U.S. Pat. No. 4,826,218 issued May 2, 1989
U.S. Pat. No. 4,915,427 issued Apr. 10, 1990
U.S. Pat. No. 4,915,427 discloses and claims a phase controlled, sequential gripping tube fitting particularly suitable for use on heavy walled tubes. The arrangement disclosed in the patent obtains proper pull-up action in a two ferrule fitting for heavy walled tubes by using ferrules having a relatively heavy and substantial construction including heavily flanged rear end portions. In addition, the coupling nut portion surrounding the ferrules is arranged to closely enclose the flanged rear end portions of the ferrules.
While the described arrangement works very satisfactorily, it would be more desirable to obtain equivalent functioning with lighter weight ferrules without relying on the heavy rear flange design.
The subject invention provides an arrangement which overcomes the above-discussed disadvantage of the prior design and allows relatively light weight ferrules to perform satisfactorily with heavy walled tubing by controlling and containing the ferrule swaging action in a manner which prevents undesirable ferrule deformation. The design prevents excessive xe2x80x9cbear clawxe2x80x9d deformation of the rear ferrule and assures that the rear ferrule transmits the necessary driving forces to the front ferrule prior to full engagement of the rear ferrule with the tube.
In accordance with a preferred form of the invention, a phase controlled, sequential gripping tube fitting including a main body having a cylindrical tube end receiving opening with a tapered camming mouth forming the entry to the opening has a front ferrule with a tapered forward nose surface in engagement in the camming mouth and a rear surface with a conically tapered recess that extends forwardly toward the nose surface. A rear ferrule having a conically tapered nose is positioned so that the tapered nose extends into the conically tapered recess of the front ferrule. The rear ferrule further includes a rear force engaging surface. Threadedly connected to the main body is a coupling nut engaged with the rear force receiving surface of the rear ferrule to drive the rear ferrule axially forward into the conically tapered rear surface of the front ferrule and produce radial inward movement of the nose portion of the rear ferrule as well as radial inward movement of the nose portion of the front ferrule. The assembly includes an improved arrangement to control outward buckling of the rear ferrule. The arrangement includes a cylindrical central body on the rear ferrule with the central body located between the nose portion and the rear force receiving surface. Associated with the central body is a cylindrical flange portion formed on the front ferrule and extending axially rearwardly therefrom at a location radially outward of the rear recess of the front ferrule. The cylindrical flange has a cylindrical interior surface that closely surrounds the cylindrical central body of the rear ferrule to limit radial outward movement of the rear ferrule or portions thereof.
The arrangement between the nose and central body of the rear ferrule and its relationship to the axially rearward extending cylindrical flange on the front ferrule results in containment of the rear ferrule and anchors it against toroidal torsion which can produce the xe2x80x9cbear clawxe2x80x9d deformation. In addition, it is believed that by moving the contact and force transmission point forwardly into the body of the front ferrule, the front ferrule is driven move smoothly and with less radial deformation. This result can be further enhanced by closely containing the rear portion of the front ferrule by providing the coupling nut with an interior cylindrical surface which substantially engages and closely contains the front ferrule against outward radial deflection.
A principal object and primarily advantage of the invention is that it allows the use of lighter weight ferrules than was previously possible when engaging heavy weight tubing.
A further object of the invention is the provision of an arrangement for use in a phase controlled, sequential gripping tube fitting to eliminate undesired torsional rotation in the rear ferrule even when a relatively light weight ferrule is used.
Yet another object of the invention is the provision of a phase controlled sequential gripping tube fitting that is especially suited for heavy walled tubing but which can also be used for standard weight tubing.
Still other advantages and benefits of the invention will become apparent to those skilled in the art upon a reading and understanding of the following detailed description.